With an ever increasing demand on the built environment to meet EU carbon emission targets, why are green facades – given
their potential benefits – not implemented more extensively in the UK?
Carbon Emission Targets
It is ubiquitous knowledge that the earth is changing as a result of thousands of years of neglect from
mankind, as finite resources are depleting and the world is becoming ever more polluted. This global issue
has become increasingly pressing with greater urbanisation and the unsustainable consumption which is
part of this. Cities may cover only 2% of the earth’s surface, but within those cities live 50 % of the
world’s seven billion people who account for 75% of humanity’s annual resource consumption.1
The construction industry and built environment are responsible for 30-40% of the world’s carbon
emissions through construction, maintenance, use and demolition; 64% of this comes from heating
alone.2
Bodies such as the EU have taken action to offer strict targets and levels to be achieved in order to ensure
that its member states take the adequate moves towards a sustainable future instructing them to cut
Greenhouse gas emissions (GHG) by 80-95% by 2050, from the 1990 figures.3
Climate Change Act 2008
The Climate Change Act was subsequently passed in the UK to be the first legally binding target for the
reduction of at least 80% of emissions. Working together with the Committee on Climate Change (an
independent advisory body) a road map was devised outlining the strategies to meet the EU 2050 levels,
addressing primarily waste and efficiency of infrastructure and the built environment,
Given that 43% the UK’s GHG is derived from building heat loss and wasted energy,4 the built
environment routemap outlines the strategy for the installation of “proven and cost effective
technologies”5 to improve energy efficiency and reduce waste, retrofitting existing building stock with
technologies compliant with the EU regulations and targets, but also looking into the broader spectrum
of the construction industry and means to reduce reliance on unsustainable resources and practices.
Grant, G., Ecosystem services come to town pp. , 5
Low Carbon Routemap for the UK Built Environment, 5 Mar 2013, the Green Construction Board pp. 14
3 http://ec.europa.eu/clima/policies/brief/eu/index_en.htm
4 https://www.gov.uk/government/policies/helping-households-to-cut-their-energy-bills/supporting-pages/greendeal
5 The Carbon Plan: Delivering our low carbon future, HM Govt, December 2011, pp. 4
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These ‘proven and cost effective technologies’ however offer no opportunity for exploration of
innovative systems, which may be more efficient, meeting several demands with one installation. This is
the potential of building greening, or more specifically, vegetated façades:
“Building integrated vegetation… is not an optional extra, gimmick or passing fancy but one element of a whole suite of
measures which should be used to restore ecosystems and help us move towards life within natural limits.”6
In spite of known attributes of the green facades, there is no encouragement or suggestion of this kind of
system as an alternative solution to reducing energy consumption and carbon emissions.
Potential Environmental Benefits
“A roof or external wall can be more than just a weatherproof surface or structural element – it can be a
living, cooling, cleansing skin.”7
This section of the report aims to outline the potential environmental benefits associated with green
façade infrastructure in a temperate climate.8
Evapo-transpirative Cooling / Shading
Plants naturally respond to diurnal, seasonal and climatic changes to maximise efficiency of
photosynthesis, transpiration, evaporation and respiration; these innate biological functions can intuitively
work with building systems to help naturally cool, shade and protect the building and its occupants. Fig X
illustrates the seasonal changes to the evergreen plant structure, as in winter the leaves close down to
enclose the stagnant air (performing as an insulative layer), while in summer the leaves rise, ventilating the
gap and cooling it with the vapour release as a product of evapo-transpiration.9 [Deciduous varieties
which drop their leaves in winter lose the effective air layer however increase exposure to sun, a critical
feature of south/west facing façades.]
Comparative to conventional shading devices, research studies have observed that green facades perform
more efficiently on account of the “lower surface plant temperature” and as only 5-30% of incident
radiation reaches the wall behind the foliage while 5-20% is used for photosynthesis a, 10-50% is
converted into latent and sensible heat, with only 5-30% reflected.10 This can reduce reliance on active
Grant, G., Green Roofs and Façades, IHS BRE press, 2006 pp. ix.
Grant, G., Green Roofs and Façades, IHS BRE press, 2006 pp. 2.
8 The benefits of façade greenery largely vary depending on climate and for the purposes of this report in analysing
why the systems are not more widely used in the UK, the benefits listed will be those applicable to temperate
climates. See Appendix for potential in hotter climates.
9 Green Design: Agnes Novak pp 47-8
10 M. Ottelé et al. / “Comparative Life Cylce Analysis for green façades and living wall systems” Energy and
Buildings 43 (2011) 3420
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systems such as air conditioning units to cool buildings with up to 23% energy savings and 8% annual
cost savings. This clearly evidences the system as highly valuable and sustainable, however it can be
questioned whether such shading devices are required in a temperate climate such as that found in the
UK. The validity of such benefits may perhaps be more pertinent warmer climates, and even more so
when incorporated with glass facades to maximise daylight but mitigate heat gain.
Manfred Köhler observed that the shading effectiveness is dependent on the density of the leaves, noting
that Ivy was the most efficient as the density was comparable to that of trees.
However:
University of Brighton 2003 Bioshader experiment


Thermal shading effect of climbing plants on glazed facades
two university rooms, of same size, same glazing area, orientation and occupancy; one installed
with Bioshader
 few degrees warmer than rest of UK, rarely below -5°, coastal winds,
 Virginia Creeper, tall, fast spreading, little maintenance.
 Results: solar transmittance 0.43 – 0.14 between one and five layers of leaves; internal
temp reductions of 3.5 – 5.6°C (37-86% reduction of solar radiation)
Water Attenuation
Green façades can, like green roofs, help in the drainage of dense inner cities clogged with the hard and
non-porous materials of the built environment. Integrated into urban planning as part of Sustainable
Urban Drainage Systems (SUDS) such measures can help to alleviate the effects of extreme rain, an ever
more common and unpredictable effect of climate change.
Rubens Hotel, Victoria London, 2013
Completed in August 2013, this living wall by Gary Grant Consultancy is the most recent addition to
London’s Green Infrastructure campaign bolstered by Mayor Boris Johnsons Businsess Improvement
Districts (BIDs) programme. Two months of construction, 16 tonnes of soil and 10 000 plants of 20
species spread over a 350m2 facade have been installed with Scotscape Living Wall manufacturers
primarily as a conscious attempt to address concerns for flooding in London city centre. This was
following an audit by the Environment Agency which indicated that 534 000 buildings in London were
on the Thames floodplain, a quarter of which were at risk of flooding. Claims have been made that the
wall will be capable of harvesting up to 10 000 litres of water, which will then be fed through the living
wall for irrigation. As the largest living wall in the UK to date, it is still to be subjected to strict critique of
its performance, not only for water attenuation, but also increasing biodiversity in the city centre,
reducing air pollution and enlivening the dense urban environment.11
Insulation
Many existing studies examine the effectiveness of green facades in hotter climates, where they work to
cool the buildings, however in cooler climates and seasons the stagnant air layer between the vegetation
and façade can perform as another insulative layer. Perini et. al. confirmed this when investigating the
effect of air flow around greened façade which showed that the thermal resistance of a direct greened
11
http://www.dezeen.com/2013/08/21/londons-largest-living-wall-will-combat-flooding/ 19/10/13
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façade was increased by 0.09m2K/W. 12 Similar to a vegetative wind break, the green façade acts as a
barrier, protecting the façade from the wind and minimising thermal transmittance directly along the
building envelope. This is particularly important for temperate climates…
University of Sheffield Study
The University of Sheffield working together with living wall system manufacturer Scotscape has installed
four different types of green wall in order to challenge the lack of quantitative analysis of the performance
of vertical greenery systems in the UK. The project is expected to recover results in autumn 2013, and fill
an important gap in UK literature enabling the profession and public alike to assess the benefits of these
systems with each season. This will, if successful, allow for the wider implementation of these systems
into the built environment.
Urban Heat Island Effect (UHIE)
While insulation and heat retention is important during winter seasons, dense urban cities in the UK as
elsewhere are becoming subject to the effects of the Urban Heat Island phenomenon, where
temperatures are amplified in the hard urban landscape, compared to rural surroundings and where air
flow is difficult due to urban canyons.
While many studies focus on hotter and more humid climates (many in the dense cities of Asia)
comparative studies of other climates demonstrate how building greenery can effectively mitigate the
effects of this, and while this is more effective in hotter drier climates, temperature differentials of
between 1.7° and 3.2° can have a significant impact on the occupants who are unused to the temperature
fluctuations in temperate climates (these figures refer to Moscow and London).13 The vegetation is a
natural softening element to the environment, with lower reflectivity of solar radiation and the higher
humidity levels resulting from evaop-transpiration also help to reduce high urban temperatures.
Dust Mitigation
Another biological function of plants is the absorption of carbon dioxide from the air, to be replaced with
oxygen, which have obvious benefits to improve the air quality in dense polluted cities. However they are
also effective and proven to be naturally adept at mitigating particulate matter in the air.
A great deal of controversy arose in 2012 when the UK government was confronted for having breached
EU laws setting NO2 levels (initially established in 1999), in 34 of its 43 zones, with monitors showing
that the “long-running urban traffic locations have not improved since monitoring began 15 years ago”.14
Worryingly, “air pollution is the biggest public health risk after smoking” which causes asthma in children,
putting the over 65s at risk of cardiovascular disease costing the government at least £8.5 billion every
year.15 In 2010 London had the fourth highest levels of PM2.5 and PM10 in the EU, which can be inhaled
causing lung damage and respiratory problems, and the “highest annual mean concentrations of NO2, a
Katia Perini, Marc Ottelé, A.L.A. Fraaij, E.M. Haas, Rossana Raiteri, Vertical greening systems and the effect on
air flow and temperature on the building envelope, Building and Environment, Volume 46, Issue 11, November
2011, Pages 2293
13 E. Alexandri, P. Jones / Building and Environment 43 Temperature decreases in an urban canyon due to green walls and
green roofs in diverse climates (2008) 490-91
14 http://cleanairinlondon.org/wp-content/uploads/CAL-256-Update-re-AQ-results-2012_300913-V21.pdf
15 Barry Gardiner, MP quoted on http://www.theguardian.com/environment/2012/apr/24/boris-johnson-londonair-pollution
12
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toxic gas, of any capital city in Europe in 2010 with levels comparable to Beijing before it took action for
the 2008 Olympics.”16
Vegetation is legitimately proven to help to mitigate the effects of this, as the pollutants and particulate
matter stick to the stomata on the leaves, removing it from the air, and then either dropping to the
ground in winter or being washed away in the next rain. This is again dependent on the density of the
leaves, but also their texture and size; Köhler noted that Hedera Helix is most efficient removing 6g/m2
however this has been disputed in other studies.17
Case Study: Edeware Tube Station, Marlybone Road. London, 2011
The installation of a living wall at Edgware Tube Station is part broader Green Infrastructure (GI)
implementation programme in London to address numerous concerns with the adverse effects of climate
change in the inner city however in this instance the wall has been installed to directly tackle elevated
concerns with air pollution.
The project has been funded directly by the Department of Transport and the Clean Air Fund (CAF)
who assigned Transport for London (TfL) £5m grant to implement quick measures in sites of exceeding
particulate matter (PM) and NO2.
The 200m2 wall, facing SSW has been designed with 15 species of evergreen and perennial plants which
will remain green year-round, both for reasons of appearance and most efficient particulate mitigation,
however it was noted that information was limited prior to installation of the effectiveness of plants in
hydroponic systems, and so it must be recognised that this installation is testing available information.
“This study recognises the costs and trade-offs of implementing green infrastructure, but also the wider
benefits to both human communities and the ecosystem as a whole that urban greening can provide.”18
Nature and Psychology
Increased urbanisation not only has detrimental effect to the populations of the city through the physical
effects of poor air quality, the urban heat island effect and flash weather storms but also presents a
distinct lack of space for greenery within our cities, which affects the human population psychologically
too.
It is another part of our natural instincts to survival to feel more contented when in sight of greenery;
indeed it has been scientifically proven that urban green space can significantly enhance a sense of
psychological well-being. In 1984 Roger Ulrich measured the recovery time of patients recovering from
gallbladder surgery with one set positioned in a (control) room with a window facing to a brick wall, and
another looking out to trees. The study recorded noticeably faster recovery times in the room with
vegetative view but also a lesser dependence on the use of painkillers in their recovery.19 This is evidence
of the significant merit there is in greening out our cities, addressing not only the physical sustainability
and climate change but also ensuring that in doing so, it is a desirable and thus sustainable place to live.
http://cleanairinlondon.org/wp-content/uploads/CAL-187-EC-rejects-time-extensions-in-12-UK-zones2806122.pdf
17 Shackleton, K., Smith, H., Davies, L., Bell, N., The role of shrubs and perennials in the capture and
mitigation of particulate air pollution in London. Imperial College London.
18
Shackleton, K., Smith, H., Davies, L., Bell, N., The role of shrubs and perennials in the capture and
mitigation of particulate air pollution in London. Imperial College London. 26.
19
Environmental Psychology: An Introduction pp. 50
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Biodiversity
“Biodiversity loss is moving ecological systems ever closer to a tipping point beyond which they will no longer be able to fulfil
their vital functions.” UN Secretary-General Ban Ki-moon, International Day for Biological Diversity, 22
May 2010.20
Planting green roofs book - pp 198 biodiversity
Increased urbanisation also plays risk to the sustainability of our natural world, as it cannot adapt to
climate change, and urban habitats are also destroyed by the built environment. This is “a not
unimportant consideration given the frequently reported plight of the bumble bee and the resulting
impact on pollination.”21 The last 30 years has also seen 55% reduction in butterfly populations, 60% bird
numbers and 39% of habitats and 27% of ‘priority species have dropped and continue to do so.22
It is the duty of cities to recover species, providing them with adequate habitat to conserve them for
future generations before lost forever. With a shortage of space the logical solution is to green the space
which has yet to be covered and is in abundance in city environments – the roofs and facades of buildings.
Case Study: M&S Food, Green Wall, Lewis & Hickey Architects, Sheffield
The range of opportunities offered by the implementation of green facades in reducing the dependence
upon mechanical systems is clear; however it must be clear of the ambitions of the project, and the
intentions for its employment, to ensure successful sustainability. Proven as a legitimate passive device, it
suggests that other factors are responsible for their tentative emergence in the UK.
Social Interaction
‘Unless one merely thinks man was intended to be an all conquering and sterilizing power in the world,
there must be some wise principle of coexistence between man and nature, even if it has to be a modified
kind of man and a modified kind of nature.
This is what I understand by conservation’ (Elton, 1958; p. 145). 23
History
The greening of buildings takes precedence thousands of years ago, in Mediterranean climates, which
benefitted from the cooling of the vegetation, but also in northerly regions, where turf was packed onto
roofs and walls to protect them from the harsh cold weather. More recently however there has been a
stronger association of plants with large rural residential buildings.
With increased urbanisation however, man and nature become further detached. In the late 19th century
Ebenezer Howard’s utopian idea of harmony of the two through the Garden City Movement endeavoured to
address this with plans for self-sustaining satellite towns, integrated with green space and transport
infrastructure to connect all, though this failed to make a deep impression.
20
M&s ambitions biodiversity p 6
http://sustainmagazine.com/think-greenfrastructure/ 19/10/13
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M&s ambitions biodiversity p 5
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23
Urban reconciliation ecology: The potential of living roofs and walls 1429
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As urbanisation continued so did man’s connection to nature, and there re-emergence of plants and
buildings appeared in the 1970s coinciding with the global awareness of climate change, and the role of
‘green’ buildings in potentially tackling this. Again though, architects and artists such as Hundertwasser
increased awareness of the ideas, but little work was carried out to develop technologies.
Since then the attitude towards facade greenery is making a slow shift, from being largely dominated by
an aesthetic ambition, to now looking to it as a technically viable system to address the effects of climate
change.
System trends – extensive direct > intensive hydroponic
Biodeterioration
Opinions are largely formed on the basis of these traditional systems and associations of where they are
found and the potential damage they can do; it is very true that often “Ivy and ruins go together in the
imagination like strawberries and cream”.24 The picturesque image of the ruin conjures images of the
destructive nature of the plants, which completely invade a ruined structure.
The uncomfortable association is not completely unfounded, as traditionally the plants which climbed
directly onto the walls would penetrate mortar cracks, and when aerial roots became embedded in the
structure and developed into true roots, structural problems may have incurred. However fewer systems
today employ direct attachment and cladding is more resilient. A recent study by the University of Oxford
in 2010 investigated the potential harm of Hedera Helix on limestone and noted that on removal the
limestone was undamaged and in face the aerial rootlets cleaned the stone of soiling, with little to no trace
of attachment.
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People are also uncomfortable with the thought of planting and conservation however while “Heritage
considerations must always be taken into account, and planting must avoid concealing any part of façades
with historical or aesthetic importance” planting should be seen to enhance an urban area and not be
detrimental to it. Also with the vast shortage of space in our cities, green walls offer the opportunity to
enliven a wall and urban space at ground level, which cannot be achieved with green facades.
The other systems also cast doubts on the issue of green facades, especially as the other end of the
spectrum to today’s ambition for sustainable building is that the creations of French Botanist, Patrick
Blanc, whose vivid tapestries of plants boldly line other large blank urban city walls. His main premise is
not driven by sustainability, but rather the pleasing aesthetic art which he can create. And yet his work is
higher profile, and as it is not legitimately efficient, on account costs, construction and benefits, such
systems are perhaps viewed to be more of a trend, with little sustenance.
Case Study: Paradise Park
However for people to overcome their “cultural inhibitions”25 green infrastructure “can only succeed
where this corresponds to their citizens’ new way of life”.26 This ambition is difficult however when the
human race has become so city-centric, focussed on necessity, convenience and disowned responsibility
for the earth as their own.
24
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 pp. 231
Dunnett, N., Kingsbury, N., Planting Green Roofs and Living Walls, Timber Press, London 2008 pp. 192
26
Urban Green pp.11
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Green facades pose a problem in that they are nor, nor cannot be community maintained, are they are not
inhabited, and maintenance is not possible without the aid of external devices. This is something lost not
only in the system but also in contemporary mentality, as with urbanisation a sense of due care and
maintenance of your space and that around you; shared space today is simply maintained by ‘someone
else’.
It is the duty of the profession to advise and advocate the use of vertical greenery systems, and while this
may at the moment be a tentative push, by tackling first the larger corporations, and national bodies
which have considerable influence over public opinion (such as the transport systems, schools and
hospitals), as a means of weaning the public round to the idea. Concurrently the profession must not only
look at retrofitting these systems to existing buildings, but consider ways to imbed them within designs,
so that sustainability is integral to the design. Green facades need not be the “veneer of green
respectability” but can be rooted much deeper in the understanding of generating a sustainable society.
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